Methods of x-ray diffraction, electron microscopy and optical diffraction are being used to study the structure and action of three multisubunit enzymes: aldolase from rabitt muscle, glutamine synthetase for E. coli, and ribulose-bisphosphate carboxylase from tobacco. The regulation of transcription of genes coding for enzymes of nitrogen metabolism by glutamine synthetase is being studied by electron microscopy. BIBLIOGRAPHIC REFERENCES: D. Eisenberg, Z. Burton, M. Blumenberg, B. Magasanik, S. Streicher, and B. Tyler. "Binding of Glutamine Synthetase to DNA" in Molecular Mechanisms of Gene Expression, (ed. by D. Nierlich and W. Rutter). Academic Press. 171-176 (1976). W.J. Scanlon and D. Eisenberg. "A High Hydrate of Acetylcholine". Biochem. & Biophys. Res. Comm. 72, 1285-1291 (1976).